Dental impression parting tool



June 9, 1936. L. KALVlN v DENTAL IMPRESSION PART-ING TOOL Filed Aug. 10, 1954 Patented June 9, 1936 UNITED STATES PATENT OFFICE Q 6 Claims.

This invention relates to parting tools useful in deeply scoring or slotting the partially set plaster or other composition in the course of taking dental impressions, so as to facilitate the separation of such impressions into predetermined segments along definite parting lines.

Supporting trays to hold the plaster in the act of applying to the dental arch are already known, in which grooves or ridges are formed in the tray for weakening the plaster impression along those lines on which it is to be parted. Where the denture is incomplete, the space where teeth are missing results in a solid wall of plaster into which such parting partition ridges do not penetrate sufficiently deep to ensure the breaking of the impression on the predetermined line.

The general purposeof the present invention is to provide a tool or instrument by which the plaster, at portions where teeth are missing, may be supplementally treated to produce or'extend the parting groove suficiently deep to ensure the parting of the cast on the desired line. Essentially, the device employs a loop-formed member which may readily be passed through a slitted portion of the tray, so as to penetrate the partially set plaster where teeth are missing, and moved transversely to form a definite groove or cleavage space and ensure the parting of the impression along the desired line. To facilitate the use of this loop-formed member, the invention comprises in its preferred embodiment a special holder by which the tool may be adjusted to convenient angles or positions with respect to a handle. A still further feature of importance in the preferred embodiment of the invention is an adjustable stop or depth gage by which the extent of penetration of the loop element may be adjusted and predetermined.

A preferred embodiment of the invention is illustrated by way of example in the accompanying drawing, in which Figure 1 represents a perspective view showing the upper surface of a dental impression of an incomplete upper dental arch, as it would appear if removed unbroken from the subject to be reproduced. I

Figure '2 is an underneath View of the tray showing the parting partition grooves and the slot through the tray at the portion where teeth are missing in the subject.

Figure 3 is a detail sectional elevation showing the loop member of the parting instrument inserted into the partially set plaster through the slot in the supporting tray.

Figure 4 is a side elevation of the complete parting tool in a preferred form.

' Figure 5 is a vertical section thereof on the line 5-5 of Figure 4, with the parts somewhat enlarged, and

Figure 6 is a diagrammatic view illustrating the adaptability of the loop member to follow a curved slot in the supporting tray.

Referring in detail to said drawing, I0 indicates a barrel or-handle formed at one end with 10 the flaring socket I I to receive the draw-in chuck or collet I2 which is moved inwardly or outwardly by operating the knurledthumb nut I3 on the end of rod I4, as clearly shown in Figure 5. a The collet I2 is in the form-of a tubular member longitudinally split or slotted on one or a plurality of lines extending part way' of its lengthfand is shaped to receive the ball head I5 from which extends the neck I6 terminating in across-bar I! in which are mounted the twoends of a looped wire I8. A knurled-headed stop screw I9 is ad justably threaded into the neck and ball members so as to be adjusted inwardly and outwardly within the loop member I8 for the purpose of varying the distance between the head of the stop screw and the endof the loop.

The construction described admits of the loop member I8 being set at varying angles with respect to the handle axis, by loosening the engagement of the collet I2 with the head I5 and shifting the loop into the desired position, as'indicated by the dotted lines in Figure 4. The loop may be turned on its own axis in any of its angular positions with respect to the handle axis, and it will thus be apparent that a substantially universal adjustment of the loop with respect to the handle is provided. One or more of the slots provided in the collet may be sufiiciently Wide to'admit of the neck portion I6 being moved into a position at right angles to the handle axis, or 40 even lower if desired, or suitable recesses or apertures may be specially formed in the collet mem-' ber to serve this purpose. The embodiment illustrated shows such an aperture in the form of an enlargement 20 of one of the longitudinal slots of the collet.

By referring to Figures 2, 3 and 6, it will be understood that in use the loop member I8 is projected through a slot 2] formed in the tray 22 which holds the plaster, to a depth depending upon the adjustment of the stop screw I9 which abuts against the bottom of the tray and thus limits the depth of penetration into the partially set plaster. Having inserted the loop member I8 into the plaster, the implement may then be linovedalong the slot 2|, whose length has been selected to conform with the length of the space where teeth aremissing. By this movement the plaster is separated over a predetermined length and at a predetermined depth, the instrument being then withdrawn and the plaster being al- "lowed to set in this, condition. 'As shown in Figure 6, the loop form of construction employed admits of the parting tool following a within the line of the parting partition ridge l5.-indicated in Figure 2 at 23, the deep groove curved line without undue resistance, and without any substantial displacement of plaster beyond the immediate vicinity of the groove which is being formed. Since the slot 2| may be formed formed in the plaster by the parting tool will be a continuation of the shallow grooves formed in the plaster by the parting partition ridges oi 'the trayr The length of the slot2l and the position of the stop screw l9 are so chosen that the moldin surface of the, plaster is not disturbed by the "parting tool coming inr contact-with either the r V ,teethorjwith the where teeth are lacking.

25 sentsa molding space of the gum surface between the tooth impressions 25, 26, is intact,

As shown in Figure 1, space 24,-which reprealthough the plaster beneath the surface 24 may be deeply grooved,,ras shown at 25 in Figure 3.

' By'adjustment of the position of loop IS with "respect to the handle I0, as already described, theimplement is readily accommodated in use "to substantially anyipart of the mouth where teeth may be missing. a V r 7 While the construction of the various parts has been particularly designed with a. view to E their mutual cooperation in the performance of thewfunction' intended, they are susceptible to useful application, without necessarily following the particular details of, construction shown.

" For example, the stop member l9 and the adjustable head mounting with respect to the handle'mayrfind useful application in conjunction with modified forms of parting elements "sub stituted for the loop 1.8 herein shown. Thus .a single pin or a 'pair'of pins, representing one ,or iboth sides of the loop, may in many respects serve a useful purposeinv an instrument for this class of work, and the stop member l9, on the other hand, may be omitted, or some other construction of stop member substituted therefor.; In its preferred form, however, the invention comprisesthe combination oi these various forms of elements cooperating substantially in f the manner described. The continuous, or uninterrupted loop of wire I.8,havinga curved outer contour and firmly secured at its ends in the '5 V cross-bar l1, provides a good rigid construction with a small amount of surface in contact with the plaster, and hence hasvery littletendency to drag or be deflected from its intended course while forming the, deep groovewithin the partial- 10 1y set plaster.

I claim:-- V a V 1. A parting tool for dental impressions, comprising a loop member'adapted to pass through 7,

a slit in asupporting tray and penetrate the 15 partially set plaster, and a stop member for abutting against the tray and arresting the loop member at apredetennined depth of penetration. 2. A parting tool for dental impressions, comprising a loop member adapted to pass through 20 a slit in a supporting tray forpenetrating the V 7' partially set'plaster, and .a handle in which said 7 loop member is adjustably secured.

3. A patring tool for dental impressions, comprising. a loop member for penetrating the par- '25 V tially set plaster, and astop member disposed within said loop member for limiting such penetration to a predetermined 'depthj 4. A parting tool for dental impressions, comprising a member for penetratingthe rpartiallytfl V set plaster, said member, havingan open space 7 between its lateral edges, and an adjustable stop neck portion with cross-bar in which the ends a5,

of said wire member are mounted, and a handle having. adraw-in collet engaging said ball memberand recessed to receive the neck portion of" V l said ball member in the angular adjustment of the wire member with respect to the handle axis. 50.

Lo IsKALvINL F 

